EVIDENCE OF INORGANIC CHLORINE GASES OTHER THAN HYDROGEN-CHLORIDE IN MARINE SURFACE AIR

We report the first measurements of inorganic chlorine gases in the ma rine atmosphere using a new tandem mist chamber method. Surface air wa s sampled during four days including one diel cycle in January, 1992, at Virginia Key, Florida. Concentrations of HCl (including HCl, ClNO3 , ClNO2, and NOCl) were in the range 40 to 268 pptv and concentrations Of Cl2 (including Cl2 and any HOCI not trapped in the acidic mist ch amber) were in the range <26 to 254 pptv Cl. Concentrations of Cl2 in creased during the night, and decreased after sunrise as HCl concentr ations increased by similar amounts. The measurements suggest an unkno wn source of either HOCl or Cl2 to the marine atmosphere. Photochemica l model calculations indicate that photolysis of the observed Cl2 wou ld yield a chlorine atom (Cl.) concentration of order 10(4)-10(5) cm-3 . Oxidation by Cl. would then represent a significant sink for alkanes and dimethylsulfide (DMS) in the marine boundary layer. The cycling o f Cl. could provide either a source or a sink for O3, depending on NO( x) levels.